This invention relates generally to gas turbine machinery and specifically, to a multi-nozzle, dual-fuel can combustor with a center nozzle surrounded by outer nozzles for use in land-based power generation gas turbines.
Gas turbines generally include a compressor, one or more combustors, a fuel injection system and a multi-stage turbine section. Typically, the compressor pressurizes inlet air which is then turned in direction or reverse-flowed to the combustors where it is used to cool the combustors and also to provide air to the combustion process. In some multi-combustor turbines, the combustors themselves are located in a circular array about the turbine rotor, in what is generally referred to as a “can-annular” array, and transition ducts deliver combustion gases from each of the combustors to the first stage of the turbine section.
More specifically, in a typical gas turbine configuration, each combustor includes a generally cylindrical combustor casing secured to the turbine casing. Each combustor also includes an internal flow sleeve and a combustor liner substantially concentrically arranged within the flow sleeve. Both the flow sleeve and combustor liner extend between a double-walled transition duct at their downstream ends, and a combustor liner cap assembly at their upstream ends. The outer wall of the transition duct and a portion of the flow sleeve are provided with air supply holes over a substantial portion of their respective surfaces, thereby permitting compressor air to enter the radial space between the inner and outer walls of the transition piece and between the combustor liner and the flow sleeve, and to be reverse-flowed to the upstream portion of the combustor where the airflow is again reversed to flow through the cap and into the combustor.
Dry low NOx (DLN) gas turbines typically utilize dual-fuel combustors that have both liquid and gas fuel capability. One common arrangement includes four dual-fuel nozzles surrounding a center dual-fuel nozzle. The combined capability for flowing liquid fuel, atomizing air, dilution water, diffusion gas, premixed gas, and sometimes air curtain/purge air, however, makes the nozzles complex and expensive, and requires a large amount of space in the premixer for the many separate fluid passages. Further, when scaling these nozzle designs to smaller machines, the space requirement of the many passages becomes increasingly difficult to manage.
Commonly owned U.S. Pat. No. 6,598,383 discloses an arrangement with a gas-only center nozzle surrounded by a plurality of outer dual-fuel nozzles. With this configuration, ignition is with diffusion fuel in the center nozzle only, and the lack of a close spark may make ignition problematic.